Find out what's tripping your RCD

Track down which circuit or plugged-in appliance is tripping your RCD, without opening the consumer unit.

RCD-01Get set up safely firstOnly touch the switches on the consumer unit — never remove its front cover, that exposes live parts. Grab a torch in case resetting the trip cuts your lights again. If you smell burning, see scorch marks, or the RCD won't reset at all, stop testing and call a registered electrician.

1 each · Torch

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RCD-02Photograph the consumer unit labellingBefore you flip anything, take a phone photo of the consumer unit door and any circuit labels. You'll be switching several breakers on and off, and you need to put everything back to the right circuit afterwards.

RCD-03Try resetting the RCD oncePush the tripped RCD switch back up. If it stays up, it may have been a one-off nuisance trip — a power cut, or two things switching on at the same moment. If it trips straight back down, there's a genuine fault somewhere and you need to carry on testing.

RCD-04Turn off every circuit breaker below the RCDSwitch off all the MCBs (the row of smaller switches under the RCD), then reset the RCD on its own. If it now stays on with everything else off, the fault is on one of your circuits, not the RCD itself.

RCD-05Switch circuits back on one at a timeWith the RCD held on, flip the first MCB on and wait a few seconds. If the RCD trips, you've found the faulty circuit — leave that MCB off. If it stays on, move to the next MCB and repeat until the RCD trips.

RCD-06Work out what's on that circuitCheck the consumer unit labelling from your photo to see which sockets, lights or appliances sit on the faulty circuit. Common labels are 'downstairs sockets', 'kitchen', 'lighting' or 'outdoor'.

RCD-07Unplug everything on that circuitPull the plug on every appliance connected to sockets on the faulty circuit. Reset the RCD and turn that circuit's MCB back on. If it now stays on, one of the appliances you unplugged is the culprit, not the fixed wiring.

RCD-08Plug appliances back in one at a timeReconnect each item individually, waiting a moment after each one. Watch for the trip when you plug in kettles, toasters, washing machines, fridges or anything that's been near water or has a heating element — these fail most often. When the RCD trips, unplug that item and don't use it again until it's been checked or repaired.

1 each · Notepad and pen

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RCD-09Suspect the fixed wiring if no appliance is at faultIf the circuit still trips the RCD with everything unplugged, the fault is in the fixed wiring, a light fitting, or an outdoor cable — often water ingress in an outdoor socket or garden lighting circuit. This needs a registered electrician to test and repair safely; don't keep resetting and using that circuit in the meantime.

RULES

KNOW THE RULES

Faults in fixed wiring should be diagnosed and repaired by a competent or registered electrician. Any new circuit or consumer unit change counts as notifiable work under Part P of the Building Regulations, and must be certified.

RCD-10Restore power and tidy upOnce you've found and isolated the faulty item or circuit, switch the remaining MCBs back on and reset the RCD. Write down which circuit or appliance caused the trip, in case it happens again or you need to tell an electrician.

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